In the greenhouse industry, certain kinds of containers are required to hold soil and waters for growing plants. During the period of rooting, cuttings or starting seeds, there is not much space required for arranging a plurality of such containers. In fact, these containers can be placed very closely with each other. When the plants grow bigger, a prescribed spacing among adjacent plants is required to provide optimum air and light so as to assure better growing of the starter plants before the starter plants are sold to the customers, and are finally separated.
To maximize the effective use of the greenhouse space and provide optimum spacing, the growing trays with adjustable spacing are in demand. For example, a product known as ECO TRAY.RTM. has been manufactured and sold in the market by Knipping BV, a Dutch company. The ECO TRAY.RTM. is a molded plastic tray that has two rows of tray compartments in each piece. The trays are arranged one piece adjacent to another and kept with the prescribed spacing between the adjacent pieces by a bar called ECO-plug.RTM.. When the plants are growing up, the trays are rearranged to adjust the spacing between them and held by a different spacing bar, i.e. ECO-plug.RTM., to maintain the adjusted spacing. The rearrangement of the trays and replacement of the spacing bars still require a lot of labor work and costs.